Question

When you open a file for the purpose of retrieving a pickled object from it, what file access mode do you use?

Short answer

Answer: The appropriate file access mode to use is 'rb', which stands for read mode in binary format.

Step-by-step solution

Understand pickling in Python

Pickling is the process of converting a Python object into a byte stream, which can then be saved to a file or sent over a network. Unpickling is the inverse operation, where the byte stream is loaded back into a Python object. The 'pickle' module in Python is used to perform these operations.

File access modes in Python

When opening a file in Python, we can specify the access mode using a string. Here are some common file access modes: - 'r': Read mode - for reading the contents of an existing file - 'w': Write mode - for writing new content or overwriting existing content in a file - 'a': Append mode - for appending new content to an existing file - 'x': Exclusive creation mode - for creating a new file, but raises an error if the file already exists - 'b': Binary mode - used as an additional flag for processing binary files - 't': Text mode - used as an additional flag for processing text files (default if not specified)

Determine the appropriate file access mode

Since we want to retrieve a pickled object from a file, we need to read the contents of the file. Pickled objects are stored in binary format, so we need to read the file in binary mode. Therefore, the most appropriate file access mode would be 'rb' ('r' for read and 'b' for binary). To open and unpickle an object, the following code can be used: ```python import pickle with open('file_name.pkl', 'rb') as file: unpickled_object = pickle.load(file) ```